阅读说明：本技术 一种柠檬酸发酵尾渣的综合利用工艺 (Comprehensive utilization process of citric acid fermentation tailings ) 是由 高秀珍 马钦元 于 2019-10-24 设计创作，主要内容包括：本发明属于废弃物的资源综合利用领域,具体涉及一种柠檬酸发酵尾渣的综合工艺。首先将柠檬酸发酵尾渣进行蒸汽爆破与离子液体的级联反应,在实现菌体成份充分释放的同时,对菌体几丁质以及玉米纤维素的晶体结构进行充分的破坏,为纤维素酶和几丁质脱乙酰酶的作用提供良好的基础,同时将预处理过程中产生的可溶性糖及蛋白等副产物进行几丁质脱乙酰基酶的发酵生产,实现了一种协同的绿色生产,易于产业化应用。(The invention belongs to the field of comprehensive utilization of waste resources, and particularly relates to a comprehensive process for citric acid fermentation tailings. The method is characterized in that the citric acid fermentation tailings are subjected to steam explosion and ionic liquid cascade reaction, the crystal structures of thallus chitin and corn cellulose are sufficiently destroyed while thallus components are sufficiently released, a good foundation is provided for the effects of cellulase and chitin deacetylase, meanwhile, byproducts such as soluble sugar and protein generated in the pretreatment process are subjected to fermentation production of the chitin deacetylase, and the synergistic green production is realized, and the industrial application is easy.)

1. A comprehensive utilization method of citric acid fermentation tailings is characterized in that the fermentation tailings are citric acid fermentation tailings taking corns as raw materials and aspergillus niger as fermentation strains, and the treatment method comprises the following steps:

(1) carrying out gas explosion treatment on the citric acid fermentation tailings to obtain a soluble part and a solid residual part, wherein the solid residual part is subjected to ionic liquid pretreatment;

(2) drying the material treated by the ionic liquid, performing enzymolysis by adopting cellulase, wherein the soluble part after enzymolysis is for later use, and performing enzymolysis on the solid residue by using chitin deacetylase to produce a partially deacetylated chitosan precursor;

(3) and (3) performing fermentation production on the chitin deacetylase after air explosion and enzymolysis by using cellulase, and performing enzymolysis in the step (2) again on the produced chitin deacetylase to realize cyclic production and utilization of the chitin deacetylase.

2. The comprehensive utilization method of citric acid fermentation tailings as claimed in claim 1, wherein the conditions of the gas explosion pretreatment are as follows: the water content of the citric acid fermentation tailings is 25-40%, the steam explosion pressure is 2.0-2.5MPa, and the time is 60-90 s.

3. The comprehensive utilization method of citric acid fermentation tailings as claimed in claim 1, wherein the ionic liquid pretreatment conditions are as follows: and drying the solid residues subjected to steam explosion pretreatment until the water content is 10-12%, treating the solid residues with an ionic liquid at the temperature of 60-80 ℃ for 6-24h, wherein the addition amount of the ionic liquid is 10-20mL per 5g of the dried material.

4. The method for comprehensively utilizing citric acid fermentation residues as claimed in claim 3, wherein the ionic liquid is tetrabutylammonium hydroxide, and the ionic liquid concentration is 20-25% aqueous solution.

5. The method for comprehensively utilizing the citric acid fermentation tailings as claimed in claim 1, wherein the cellulase enzymolysis conditions are as follows: drying the materials until the water content is 10-12%, adjusting the material concentration to 80-140g/L, carrying out enzymolysis at 40-60 ℃ for 20-32h, adjusting the pH value of enzymolysis to 4.0-5.8, and adding 20-35U/g of cellulase.

6. The method for comprehensively utilizing citric acid fermentation tailings as claimed in claim 1, wherein the enzymatic hydrolysis conditions of the chitin deacetylase are as follows: drying the solid residue after the cellulose enzymolysis until the water content is 10-12%, adjusting the material concentration to 20-50g/L, the enzymolysis temperature to 25-37 ℃, the enzymolysis time to 6-12h, the enzymolysis pHs to 5.5-7.5, and the addition amount of the chitin deacetylase to 3000-3700U/g.

7. The method of claim 1, wherein the liquid residue obtained by solid-liquid separation after steam explosion treatment and the liquid residue obtained by solid-liquid separation after cellulose hydrolysis are combined and dried until the water content is 10-12% and used as a fermentation substrate for chitin deacetylase production, which is hereinafter referred to as a "by-product";

the fermentation medium for producing chitin deacetylase consists of: 5-10g/L of yeast extract powder, 0.5-2.0g/L of by-product, 1.0g/L of magnesium sulfate, 0.3g/L of monopotassium phosphate, 1.0g/L of dipotassium phosphate, 0.5-2.0g/L of sodium chloride and pH 6.0-7.0.

8. The method for comprehensively utilizing citric acid fermentation residues as claimed in claim 7, wherein the fermentation conditions for producing chitin deacetylase by using the fermentation medium are as follows: the inoculation amount is 2-10%, the stirring speed is 160-.

9. The method of claim 8, wherein the fermentation broth is Rhodococcus, yeast, Escherichia coli, Mortierella or anthrax.

10. The method for comprehensive utilization of citric acid fermentation residues as claimed in claim 9, wherein the fermentation strain is Rhodococcus equi CGMCC NO. 14861.

The technical field is as follows:

the invention belongs to the field of comprehensive utilization of waste resources, and particularly relates to a comprehensive process for citric acid fermentation tailings.

Background art:

citric acid is the organic acid with the largest microbial fermentation yield at present, is widely applied to industries such as beverages, foods, washing daily chemicals and the like, and the used microorganism is mainly Aspergillus niger. After citric acid fermentation, a large amount of Aspergillus niger hypha residues are generated. According to industry statistics, about 0.15 tons of dry mycelia are produced per ton of citric acid produced. Currently, global citric acid production is estimated to exceed 200 million tons per year, which means that about 30 million tons of black fungus are produced per year. Typically, these tailings are treated to a low value for use as feed for ruminants.

Chitin is reported to be present in about 15% of the dry cell weight of Aspergillus niger. Therefore, Aspergillus niger mycelia are a good raw material for producing chitin and its derivatives, including chitosan, chitosan oligosaccharide, N-acetyl-D-glucosamine (GlcNAc) and glucosamine (GlcN), and have wide application in the biomedical, food, health care and cosmetic industries. However, the current mainstream process adopts chemical extraction, and has the problems of strong acid and strong alkali, environmental pollution and the like. The enzymatic preparation of chitin and its derivatives has received increasing attention as an eco-friendly process. However, enzymatic production of chitin and its derivatives remains challenging, one of the main reasons being that the crystallinity of chitin makes it insoluble in water. Therefore, the development of a reasonable pretreatment method has important significance in improving the crystal structure of chitin before the chitin and derivatives thereof are biologically converted into chitosan.

Meanwhile, most of the industrial citric acid fermentation at present adopts coarse material fermentation, and in addition to degerming in fermentation tailings taking corn as raw material, a large amount of corn fiber is contained (each Kg of dry matter comprises 382 g of cellulose, 445 g of hemicellulose, 66 g of lignin, 19g of protein and 28g of ash). Therefore, in order to comprehensively recycle the waste hyphae, the fungus body and the corn fiber should be simultaneously studied. At present, there is no report on comprehensive utilization of fibers, proteins and mycelia remained in citric acid fermentation tailings through a reasonable pretreatment mode, which is a problem to be discussed and solved under the current environment protection situation.

The invention develops a process for pretreating citric acid fermentation tailings by steam explosion and ionic liquid cascade and comprehensively utilizing different components of the citric acid fermentation tailings, and provides a possible way for comprehensively utilizing the citric acid fermentation industrial tailings.

The invention content is as follows:

aiming at the defects of the prior art, the invention aims to provide an efficient comprehensive treatment technology of citric acid fermentation tailings and application thereof.

The comprehensive utilization method of the citric acid fermentation tailings aims at the citric acid fermentation tailings taking corns as raw materials and aspergillus niger as fermentation strains, and comprises the following steps:

(1) carrying out gas explosion treatment on the citric acid fermentation tailings to obtain a soluble part and a solid residual part, wherein the solid residual part is subjected to ionic liquid pretreatment;

(2) drying the material treated by the ionic liquid, performing enzymolysis by adopting cellulase, wherein the soluble part after enzymolysis is for later use, performing enzymolysis on the solid residue by using chitin deacetylase to produce a partially deacetylated chitosan precursor, and providing a basis for preparing chitosan and chitosan oligosaccharide with high deacetylation degree by further deacetylation;

(3) the soluble part after air explosion and enzymolysis of cellulase is used for fermentation production of chitin deacetylase, and the produced chitin deacetylase is used for enzymolysis in the step (2) again, so that cyclic production and utilization of the chitin deacetylase are realized;

further, the gas explosion pretreatment conditions are as follows: the water content of the citric acid fermentation tailings is 25-40%, the steam explosion pressure is 2.0-2.5MPa, and the time is 60-90 s;

further, the ionic liquid pretreatment conditions are as follows: drying the solid residues after steam explosion pretreatment until the water content is 10-12%, treating the solid residues with ionic liquid at 60-80 ℃ for 6-24h, wherein the addition amount of the ionic liquid is 10-20mL per 5g of the dried material;

further, the ionic liquid is tetrabutylammonium hydroxide, and the concentration of the ionic liquid is 20-25% of aqueous solution;

further, the enzymolysis conditions of the cellulase are as follows: drying the material until the water content is 10-12%, adjusting the material concentration to 80-140g/L, carrying out enzymolysis at 40-60 ℃ for 20-32h, wherein the enzymolysis pH is 4.0-5.8, and the adding amount of cellulase is 20-35U/g (drying substrate);

further, the chitin deacetylase enzymolysis conditions are as follows: drying the solid residue after the cellulose enzymolysis until the water content is 10-12%, adjusting the material concentration to 20-50g/L, the enzymolysis temperature to 25-37 ℃, the enzymolysis time to 6-12h, the enzymolysis pH to 5.5-7.5, and the addition amount of the chitin deacetylase to 3000 ion 3700U/g (drying substrate).

Further, liquid residues obtained by solid-liquid separation after steam explosion treatment and liquid residues obtained by solid-liquid separation after cellulose hydrolysis are combined and dried until the water content is 10-12% and used as a fermentation substrate (hereinafter referred to as a byproduct) for chitin deacetylase production;

further, the fermentation production conditions of chitin deacetylase are: the inoculation amount is 2-10%, the stirring speed is 160-200rpm, the temperature is 30-40 ℃, and the fermentation time is 12-30 h;

preferably, the fermentation strain is Rhodococcus, yeast, Escherichia coli, Mortierella or anthrax;

more preferably, the fermentation strain is Rhodococcus equi CGMCC NO. 14861;

further, the fermentation medium consists of: 5-10g/L of yeast extract powder, 0.5-2.0g/L of by-product, 1.0g/L of magnesium sulfate, 0.3g/L of monopotassium phosphate, 1.0g/L of dipotassium phosphate, 0.5-2.0g/L of sodium chloride and pH 6.0-7.0.

In the treatment process, the release rate of soluble components in the citric acid fermentation tailings after steam explosion is improved by 15-30%; the content of soluble sugar after enzymolysis of cellulase reaches 0.4-0.53 g/g; after the enzymolysis of the chitin deacetylase, the content of acetic acid generated by deacetylation of the chitin deacetylase reaches 480-554 mg/L; after fermenting for 24h, the chitin deacetylase content in the fermentation liquor reaches 4854.7U/mL.

Has the advantages that:

the technology for cascade pretreatment and comprehensive utilization of the citric acid fermentation tailings provided by the invention can realize efficient release of various components in the citric acid fermentation tailings and provide a more appropriate substrate for subsequent enzymolysis. Through the optimization of pretreatment conditions and subsequent enzymolysis conditions, the release rate of soluble components in the citric acid tailings after steam explosion is improved by 30.2 percent, the content of soluble sugar after cellulase hydrolysis reaches 0.53g/g, the efficiency of cellulase hydrolysis is improved by 26.97 percent, chitin deacetylase shows higher activity on the inactivity of a substrate which is not pretreated, the content of acetic acid released by deacetylation reaches 554.48mg/L, meanwhile, byproducts generated in the pretreatment and enzymolysis processes are applied to the fermentation production of the chitin deacetylase, the enzyme produced by fermentation is improved by 1.5 times, and the enzyme produced by fermentation reaches 4854.7U/mL. Compared with the prior art, the cascade pretreatment process provided by the invention can realize the high-efficiency pretreatment of the citric acid fermentation tailings, realize the cooperative production of chitin deacetylase and chitin derivatives, provide a good reference for the comprehensive utilization of resources of the citric acid fermentation tailings, and have wide industrial application prospects.

Description of the drawings:

FIG. 1 is a full flow chart of the cascade pretreatment process and comprehensive utilization;

FIG. 2 is a diagram showing the effect of pretreatment of citric acid fermentation tailings under different steam explosion conditions

Wherein, A is color change; b: scanning an electron microscope picture; c: a change in porosity; d: change of soluble components;

FIG. 3 is a scanning electron microscope image of different cascade pretreatment citric acid fermentation residues;

wherein, A is 2000 times of magnification; b: amplifying by 10000 times;

FIG. 4 fermentation production curves for chitin deacetylase.

The specific implementation mode is as follows:

in order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present patent and are not intended to limit the present invention.

The process flow of the present invention is shown in FIG. 1, and the present invention will be further explained with reference to specific examples.